Circuit interrupter with thermal compensated time delay



Dec. 18, 1956 w. J. wExNr-URT 2,774,841

CIRCUIT INTERRUPTER WITH THERMAL COMPENSATED TIME DELAY Filed 061;. 22, 1952 2 Sheets-Sheet l JNVENTOR. M//z'am W/hfurt g km @JJM Dec. 18, M56 w. J. WEINFURT 297742841 CIRCUIT INTERRUPTER WITH THERMAL COMPENSATED TIME DELAY Filed Oct. 22; 1952 2 Sheets-Sheet 2 /f IN VEN TOR. W//l'am M70/iff Z United States Patent O CIRCUIT INTERRUPTER WITH THERMAL COMPENSATED TIME DELAY William J. Weinfurt, Wauwatosa, Wis., assigner to McGraw Electric Company, Milwaukee, Wis., a corporation of Delaware Application October 22, 1952, Serial No. 316,151

1 Claim. (Cl. 20G-97) This invention relates to automatic reclosing circuit interrupters of the general type disclosed in U. S. Patent No. 2,560,831 of July 17, 1951, issued to Anthony Van Ryan and Carl Schindler for Circuit Interrupter and assigned to the same asignee as the present application.

This invention has the same objects as those previously disclosed but in addition to that has for its further objects the correction for changes in viscosity of the oil or other hydraulic medium employed in the time delay mechanism.

It has been found that the oil or other hydraulic medium gets thicker as the temperature decreases and it is consequently diicult to maintain substantially the same time delay where the hydraulic medium is depended upon to produce the time delay.

This invention is designed to overcome the above noted defects and the primary purpose of this invention is to provide means for maintaining the time delay relatively constant irrespective of changes in temperature of the hydraulic medium.

A further object of this invention is to provide corrective time delay means which can be used for either delaying the opening or the closing operation of the circuit interrupter. The disclosure in the drawings shows one means of accomplishing the time delay for the opening'only of the circuit interrupter.

A further object of this invention is to provide a very simple time delay means which is so constructed that it is most easily applied to circuit interrupters now commercially available and in wide use and in which the change to the new type of device is accomplished with a minimum of eiort.

An embodiment of the invention is shown in the accompanying drawings in which:

Figure 1 is a transverse sectional View through a circuit interrupter such as that shown in the above identied patent, such view corresponding roughly to Figure 7 of the patent with the attachment applied thereto.

Figure 2 is a sectional view on the line 2-2 of Figure 1.

Figure 3 is a face view of the device removed from the circuit interrupter.

Figure 4 is a sectional view on the line 4-4 of Figure 3.

Figure 5 is an enlarged sectional detail through the valve of the device.

Figure 6 is an enlarged view of a portion of a bimetal strip.

As set forth in detail in the above noted patent, the circuit interrupter is caused to open when current in the solenoid 1 exceeds a predetermined value. This causes the downward drawing of the magnetic plunger 2 which is connected in the manner described in the above noted patent with the main switch means in series with the solenoid 1. A pump 3 pumps Huid beneath the counting piston 4 through the passageway 5 and causes the counting piston 4 to rise in a step-by-step manner. Normally the oil or other hydraulic medium trapped beneath the plunger 2 within the cylinder 6 escapes around the sides of the piston 2 into the passage 7 and causes the light piston or slide valve 8 to move upwardly, it being noted that the plate 9 covering the upper end of the passage 7 is provided with a plurality of holes 10 and that the piston or slide valve 8 is provided with a hole 11. Normally the piston or slide valve 8 rests upon a shouldered portion formed in the channel 7 and when it is raised, opens the passage 12 so that the oil beneath the piston 2 is freely discharged through the passage 12. However, after one, two or more strokes depending upon the design of the circuit interrupter, the counting piston 4 has moved to a point where it closes the passage 12 and oil then slowly leaks from beneath the piston or plunger 2 as described in the previous patent. This delays the subsequent opening or openings of the circuit interrupter.

Ordinarily the mechanism hereinabove described and as set forth in detail in the above noted patent is submerged in oil which acts as the hydraulic medium.

It is apparent that as the oil becomes more viscous that the time delay is increased. On the other hand when the oil is more fluid due to hot weather the time delay is lessened.

It is customary to provide a tapped hole indicated at 13 in Figures 1 and 2 opening into the channel 7. As described in the patent, this is normally closed by a plug. However in using the corrective device the plug is removed from the opening 13 and the screw plug 14 carried by the body 15 of the device is screwed into the opening 13. This screw plug has a passageway therein which opens into the main passage 16 of the body portion 15. The body portion is provided with an outlet passage 17 which is controlled by a rotary valve 18. This rotary valve is in turn controlled by a thermostatic member responsive to the temperature of the hydraulic medium. For instance and as shown in the drawings, the thermostatic member may be made in the form of a bimetal spiral 19 whose inner end 19 is secured in a slot 20 formed in the rotary valve 18. Preferably the top end of the slot 20 is slightly closed after insertion of the lip 19' by pinching the ends of the valve 18 together. The outer end of the bimetal strip 19 is provided with an arm 19" which 'ts within a slot 21 formed in an open revoluble shell 22 carried by the body portion. This shell is locked in place by means of a screw 23 and nut 24 so as to determine its initial setting. It is to be noted that an elongated arcuate slot 2S is formed in the shell to allow a slight rotary adjustment of the shell 22 for the initial setting. Preferably the end of the opening 16 in the body portion 15 is closed by means of a screw threaded plug 26 which may be the plug normally used to close the opening 15 in the circuit interrupter when it is not provided with the corrective device.

It will be seen from reference to Figure i that the device is relatively small and easily tits in close proximity to the magnetic plunger 2 of the circuit interrupter and is located just to the side of the main body of the structure above the anged portion 27, see Figure 1.

It is to be distinctly understood that although means have been shown for controlling the time delay to thereby prevent variations due to temperature changes for the opening stroke of the circuit interrupter, that nevertheless this means could be used for controlling the time delay for the closing stroke or in fact for both sterokes as desired. Obviously, for controlling both strokes, the opening 13 could open into the passageway 7 at a point below the slide valve 8 and for controlling the closing stroke only the main passage 16 could be placed in communication with the upper end of the passage 7 above the valve 8.

In the last mentioned case, viz, when the device controlled the time of the closing stroke only, it is obvious that the plate 9 would be replaced by a plate having suitable size and number of holes and that the hole 11 in the slide valve would be increased in size.

As described in detail in the above noted patent the counting piston 4 is intended to operate lockout mechanism after a predetermined number of operations of the circuit interrupter occurring in rapid sequence. On the other hand, it' less than the predetermined number of operations of the circuit interrupter occur in rapid sequence the counting piston will slowly settle as described in the above noted patent and Will therefore reset itself for a complete new cycle of operations,

It will be seen that a very simple type of circuit interrupter has been provided which is corrected for temperature variations to thereby maintain a substantially constant time delay irrespective of temperature variations.

It will be seen further that the device is simple to construct and may be readily applied to the circuit interrupter.

Although this invention has been described in considerable detail, it is to be understood that such description is intended as illustrative rather than limiting, as the invention may be variously embodied and -is to be interpreted as claimed.

I claim:

In a circuit interrupter, the combination of switch means, an electromagnetically operated plunger for operating said switch means, hydraulic means for controlling the rate of travel of said plunger, said hydraulic means including a cylinder for said plunger and a hydraulic medium, and temperature control means submerged in said hydraulic medium and having a body portion provided with an outlet vent communicating with said cylinder, a cylindrical rotary valve extending through said body portion and provided with means for controlling said vent and projecting at one end from said body portion, a cup shaped member adjustably secured to said body portion and surrounding the projecting portion of said cylindrical valve, and a spirally arranged bimetal member surround-ing said projecting portion and positioned Within said cup shaped member and having its inner end secured to said projecting portion and its outer end secured to said cup shaped member.

References Cited in the le of this patent UNITED STATES PATENTS 1,058,290 Corey Apr. 8, 1913 1,110,510 Peters Sept. 15, 1914 1,806,530 Giesler May 19, 1931 2,021,428 Peo Nov. 19, 1935 2,308,660 Kouyoumjian Jan. 19, 1943 2,528,197 Wallace Oct. 31, 1950 2,560,529 Van Ryan et al. July 10, 1951 2,560,831 Ryan et al July 17, 1951 2,680,170 Wallace June 1, 1954 

